1. Field of the Invention
The present invention generally relates to an image sensor, and more particularly to an image sensor with high speed and low power consumption.
2. Description of Related Art
An image sensor, such as a complementary metal-oxide-semiconductor (CMOS) image sensor, is a device that converts an optical image into electronic signals. The image sensor has been widely used in a variety of applications such as cell phones and cameras.
There is a trend of the image sensor towards a higher resolution, a higher speed or both. As the resolution increases, more pixels are disposed in a given area and parasitic loading becomes worse, thereby slowing down the readout speed with the same power consumption. There is another trend of the image sensor towards more compact circuit area (and thus lower power consumption), which is generally opposite to the trend of higher resolution. Accordingly, a designer of an image sensor should usually make a compromise between resolution and speed.
A need has thus arisen to propose a novel image sensor with higher speed, lower power consumption and reduced circuit area.